Audio alarm system

ABSTRACT

An alarm control circuit couples a plural track tape player with a plural station paging intercom system to broadcast a plurality of different messages stored on plural track tape, in response to activation of corresponding sensors to which the circuit is connected. Facilities for testing the circuit at one location with minimal disturbance of the paging system, is provided.

United States Patent [191 Gregg, Jr. et al.

[451 Dec. 31, 1974 AUDIO ALARM SYSTEM [75] Inventors: Joseph Gregg, JL, Johnston; John Paul Hannigan, Carrolltown, both of Pa.

[73] Assignee: Jab Company, Inc.

[22] Filed: Aug. 28, 1973 [21] Appl. No.: 392,325

Primary ExaminerDonald J. Yusko Assistant Examiner-Richard P. Lange Attorney, Agent, or Firm-Harvey B. Jacobson [57] ABSTRACT [52] US. Cl 340/311, 340/221, 360/12 An alarm n r l ircuit couples a plural truck tape [51] Int. Cl. H04m 11/02 P y with a Plural Station Paging intercom system to [58] Field of Search 340/310 R, 311, 221, 328, broadcast a plurality of different messages stored on 340/224, 410, 411; 360/12, 6 plural track tape, in response to activation of corresponding sensors to which the circuit is connected. Fa- [56] References Cit d cilities for testing the circuit at one location with mini- UNITED STATES PATENTS mal disturbance of the paging system, is provided.

3,310,793 3/ 1967 Takarabe et a1 340/221 14 Claims, 4 Drawing Figures 28 Power Power /l"/2 stop ,0 pp y 26 I6 J n 1 Polarity 22 aye; Revers/n? ififZr'! I and Reset Tract; /4

Changing Control Self-Latching Sens/n9 i Ufgkfi g f Control 20 0verr/ de Test Paging Control 32 System [-"NENTED I 3.858.195

sum 2 or 3 Fig.3

To Power 8 rap Device AUDIO ALARM SYSTEM This invention relates to alarm control systems responding to a plurality of condition sensors to reproduce appropriate messages stored on tape, through an existing paging system.

An alarm control system of the foregoing type is particularly suitable for underground mine installations as disclosed in prior copending application, Ser. No. 262,227, filed June 13, 1972, now US. Pat. No. 3,798,672 owned in common with the present application. In such installations, there are a plurality of sensors located at critical points to detect fire and various operational conditions of powered equipment. Also, a commercially available paging system is installed to enable audio intercommunication between personnel at remotely spaced locations. The use of a commercially available plural track, tape player as disclosed in the prior copending application aforementioned, is ideally suited for reproducing different messages in response to activation of corresponding sensors, the messages being reproduced as an audio alarm by broadcast through the paging system. There is, however, a problem in servicing and maintaining the alarm control circuit interconnecting the sensors, tape player and paging system, in an operating condition. The present invention is addressed to the foregoing problem.

In accordance with the present invention a plurality of sensing circuits connected to the sensors are energized by a power source serparate from the tape player, through a polarity reversing switch by means of which one of the sensing circuits associated with the fire sensor, is reset. The other sensing circuits are opened and closed with their sensors and are not latched closed as in the case of the fire sensing circuit. When energized, any one of the sensing circuits initiates operation of the tape player and a track changing operation that stops at a selected track corresponsing to the activating sensor. Thus, a selected message is transmitted from the tape player to the paging system.

Reversal of polarity not only resets the latched fire sensing circuit, but also performs a continuity test through an indicator lamp for the sensing circuit. The tape player may also be tested by closing of a switch bypassing the sensing circuits while another switch is opened to locally restrict reproduction in the paging system.

The alarm control circuit is further operative to stop operation of powered equipment such as a belt conveyor when tires are detected, conserves energy by intermittant deenergization of the sensing circuit in the fire sensing operational mode and automatically but temporarily disconnects the tape player from the paging system while in use.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

FIG. 1 is a schematic block diagram of the alarm control system of the present invention.

FIG. 2 is an electrical circuit diagram of the system depicted in FIG. 1.

FIGS. 3 and 4 are electrical circuit diagrams showing relay circuit details of the circuit illustrated in FIG. 2.

Referring now to the drawings in detail, FIG. 1 is a functional block diagram of the alarm control system generally denoted by reference numeral 10 that includes a power supply 12 independent of the power source for a plural track, tape player 14. The power supply 12 is connected to a plurality of sensing circuits through a polarity reversing component 16. The sensing circuits include a self-latching type 18 and a plurality of non-latching types 20. Anyone of the sensing circuits when energized initiates operation of the tape player and track changing operation through control 22 that stops when the player head (not shown) reaches a track position corresponding to the activated sensor associated with a selected one of the sensing circuits 18 or 20. A priority override control 24 determines which sensor predominates although no preset activating sequence is imposed on the system. The sensors, such as fire detectors, associated with the selflatching sensing circuit 18 have priority over the other sensing circuits 20 and initiates player operation independently of the other sensing circuits. Thus, only latched sensing circuit 18 is reset by a polarity reversal action through control 16 which activates a continuity indicator 26 for testing the continuity of the sensing circuit 18. When energized the sensing circuit stops oper ation of powered equipment through a power stop control 28.

Operation of the tape player 14 may also be manually initiated in by-pass relation to the sensing circuits by a test control 30. The tape player transmits its audio output to a paging system 32 and may be partially disconnected therefrom by the test control or automatically and temporarily disconnected while the paging system is in use to avoid message interference, by means of a cut-off control 34.

Referring now to FIG. 2, the power supply 12 includes a pair of batteries 36 and 38 interconnected in series by a current limiting resistor 40. The opposite terminals of the interconnected batteries are normally connected to positive and negative voltage lines 42 and 44 through ganged switches 46 and 48 in the polarity reversing control 16. When actuated, the switches 50 and 52 also ganged with switches 46 and 48 transfer the same battery terminals to the opposite voltage lines.

The tape player 14 is operated from its own battery 54 through the test control 30 and the sensing circuits in the relay circuit section 56 as diagrammed in FIG. 2 to which the tape player is connected by conductors 58 and 60, a fuse being placed in line 58. Conductors 62, 64, 66 and 68 transmit player head position signals from the tape player to the relay circuit section 56 correspondingto the track position of the player head. Operation of the tape player occurs whenever a positive voltage is applied to line 58, also energizing the player lamp 72 connected between the negtive terminal of battery 54 and conductor 58. Track changing operation of the tape player stops whenever a negative voltage is applied through conductor 60 from the battery 54. A double pole, double throw switch 74 alternatively connects a voltmeter 76 across the terminals of battery 54 and the terminals of the power supply 12 through voltage lines 42 and 44 so as to enable monitoring of both voltage sources.

The audio output of the tape player 14 is applied through conductors 78 and 80 to the input primary winding of a transformer 82, the secondary output winding of which is connected to the paging system 32 through output terminals 84 and 86 for local audio reproduction. Broadcast of the audio output of the player throughout the paging system is effected through the input terminals 88 and 90 respectively connected to the terminal 86 and 84, terminals 84 and 90 being coupled to the negative voltage line 44 through the relay circuit section 56 and an LC filter including the choke coil 92 and parallel connected capacitor 94. v

A normally closed switch 96 in the test control 30 is opened when actuated to disconnect terminal 88 from terminal 86 thereby localizing the output of the tape player while operation of the tape player is being tested by manually turning it on through normally open switch 98 ganged with switch 96. Switch 98 connects the positive voltage line 42 to the relay circuit section 56 through conductor 100 for this purpose. A conductor 102 from the relay section also extends to the power stop device 28 for energization thereof in a fire detecting mode of the system as will be explained hereafter. The various sensing circuits are shown in FIG. 3 wherein the positive voltage line 42 is connected to four sensor switches 104, 106, 108 and 110. A diode 112 is connected across the sensor switch 104 in sensing circuit 18 'to conduct reverse current in by-pass relation to switch 104 from the negative voltage line 44 through the continuity indicator lamp 114, resistor 116 and timer switch 122. An on-off timer 118 is also connected in series with sensor switch 104 and diode 120 across the voltage lines 42 and 44 to intermittantly open the timer switch 122 while the fire sensing circuit is energized in its operating mode to thereby conduct a pulsating current. When energized upon closing of sensor switch 104, the sensing circuit 18 conducts current from the positive voltage line 42 through timer switch 122 to the relay coil of a self-latching relay 124 completing a relay circuit through the diode 120 to the negative voltage line 44. When energized, the relay 124 closes its normally open relay holding switch 126 to connect the voltage line 42 directly to the relay coil 124 to maintain it energized. The voltage line 42 is also connected by relay switch 128 to the power stop28 through conductor 102 and through closed relay switch 130 in series with relay switch 126 current is conducted from the positive voltage line by conductor 132 to the relay coil of player control relay 134, completing a relay energizing circuit to the negative voltage line through diode 136. Energization of the relay 134 closes. its relay switch 136 to connect the positive terminal of the player battery 54 through conductor 138 to conductor 58 to operate the tape player and condition the track changing control 22 for operation through conductor 140. The tape player is thus maintained operating by the latching relay 124 upon opening of the sensor switch 104 until the sensing circuit 18 is reset. Diodes 142 and 144 are connected across the coil terminals of relays 124 and 134 to prevent unintended operation due to transient voltages.

The other sensor switches are designed to detect different operational conditions by closing in any sequence to activate sensing circuits without latching as compared to the latching of sensing circuit 18 when an emergency condition is sensed, such as fire, producing shut-down of powered equipment through power stop 28.

The sensor switches 106, 108 and 110 are interconnected between the positive voltage line 42 and the player control relay 134 by associated parallel sensing circuits through the priority override control 24 and a pair of series connected diodes 146 and 148'in each of the parallel sensing circuits. Since latching relay 124 is not energized by activation of any of the latter sensing circuits 20, operation of the tape player stops upon opening of the activating sensor switch causing the relay 134 to be deenergized.

The priority override control 24 includes an interlock relay coil 150 having three, normally closed relay switches 152, 154 and 156 in each of the three sensing circuits 20, respectively. The interlock relay 150 when energized upon closing of sensor switch 104, will therefore open all of the sensing circuits 20 as long as the sensing circuit 18 is energized giving top priority to sensing circuit 18. Interlock relay coil 158 on the other hand, is energized simultaneous with the sensing circuit activated by closing of sensor switch 106 to open its normally closed relay switches 160 and 162 respectively connected in series with relay switches 154 and 156 in the remaining two sensing circuits associated with sensor switches 108 and 110. Thus, closing of sensor switch 106, will disable the sensing circuits associated with sensor switches 108 and 110. Finally, a third interlock relay coil 164 is energized upon closing through the sensing circuit established through sensor switch 108 in series with relay switches 154 and 160 to open its relay switch 166 thereby disabling the sensing circuit established through sensor switch 110 in series with relay switches 156 and 162. Each of the interlock relay coils are connected to the negative voltage line 44 through diode 168, while diodes 170, 172 and 174 are connected across their terminals.

The sensing circuits are connected to the track changing control 22 through conductors 176, 178, and 182, the conductor 176 extending directly from the sensor switch 104 of sensing circuit 18 through timer switch 122 while the other conductors extend from the juncture of the series connected diodes 146 and 148 in the parallel sensing circuits 20. As shown in F 16. 4, the conductors 176, 178, 180 and 182 are respectively connected to the normally closed relay switches 184, 186, 188 and 190 associated with the track control relay coils 192, 194, 196 and 198 of the track changing control 22. Each of the track control, relay coils to which positive voltage is supplied through conductor 140 from the player control relay 134, is sequentially energized when its other terminal is grounded by a player head position sensor in the track changing mechanism of the tape player through conductors 62, 64, 66 and 68. When sensing circuit 18 is energized, current pulsated by intermittent opening of timer switch 122 as aforementioned is conducted by conductor 176 through relay switch 184 to a feed back preventing relay coil 200 connected by diode 202 to the negative voltage line 44 together with a second feedback preventing relay coil 204. When energized, relay coil 200 closes its relay switch 206 thereby conducting pulsating current from sensing circuit 18 to the normally closed timer switch 208 through which its associated timer 210 is energized. At the end of a timing cycle initiated by energization of the timer 210, the timer switch 208 opens to prevent recycling of the timer and the normally open timer switch 212 closes to stop the track changing operation of the tape player at a selected track position, by connecting conductor 60 to the negative terminal of the player battery through conductor 214. Similarly, current from each of the other sensing circuits 20 energize relay coil 204 closing its relay switch 216 connected in parallel to the track control relay switches 186, 188 and 190 to operate the timer 210 for stopping the track changing operation when the player head reaches a track position corresponding to the activated sensing circuit.

When a normally open sensor switch 104 closes in response to heat, the interlock relay coil 150 is energized to open its three, normally closed relay switches 152, 154 and 156, respectively connected in series with sensor switches 106, 108 and 110. Also, the sensor switch 104 connects the positive voltage line 42 through the normally closed relay switch 184 of the recorder track relay 192 to the control relay coil 200 to energize the same and to its normally open relay switch 206 that is closed as a result of energization of itsrelay coil. The timer 210 is thereby activated through its normally closed timer switch 208 to start a timing cycle present for a selected duration. At the same time the sensor switch 104 connects the positive voltage line 42 to relay coil 124 for energizing the same thereby closing its normally open relay. holding switch 126 to maintain the relay coil energized upon opening of the sensor switch 104. The normally open relay switch 130 also closed by relay coil 124 when energized completes an energizing circuit through relay coil 134 to maintain both relay coils 124 and 134 energized until reset by actuation of the polarity reversing switch 16. Energization of the relay coil 124 also closes the normally open control switch 128 connected to the power stop device such as a relay in the power drive for a conveyor belt, for example, in order to stop operation of the conveyor belt or any other power equipment.

Energization of the interlock relay 1S0 prevents simultaneous closing of relay circuits by the sensor switches 106, 108 and 110 by opening its relay switches 152, 154 and 156, while energization of interlock relay 158 prevents closing of the circuit of sensor 110. Thus, sensors 106, 108 or 110 when operative complete the energizing circuit for relay coil 134 through one or more of the interlock relay switches in the series with a pair of diodes 146 and 148 bypassing relay 124. The relay coil 134 is therefore energized either by relay 124 or by one of the sensors 106, 108 and 110 to close its normally open relay switch connecting the positive terminal of the player battery 54 to the tape player 14 through fuse 70 and to the track control relay coils to start operation of the player. At the same time, the normally open relay switch 135 is closed to complete the operating circuit of the pager system by connecting the parallel LC section 92-94 to the negative voltage line 44, placing the audio output of the player on the pager system through terminals 84 and 86 connected to the secondary winding of transformer 82 coupling the audio output line from the tape player to the paging system.

As the tape player begins operating in response to closing of sensor 104, the timer 210 initiates a timing cycle as hereinbefore stated closing its normally open timer switch 212 to connect the negative terminal of the player battery to the player for operating its track changing mechanism. Thus, the timer 210 recycles and continues to change the track in the tape player until the player head is positioned on a first track, grounding track relay coil 192 to energize the same. When energized, the track control relay coil 192 opens its normally closed relay switch 184 between sensor 104 and the feedback preventing relay coil to deenergize the same, thereby opening relay switch 206 to deactivate the timer 210. Track changing operation of the player is thereby stopped with the player head on the track corresponding to the track control relay 192. The details of the player head displacing means in the track changing mechanism are disclosed in the prior copending application, aforementioned.

When sensor 106 is closed and is in an operative interlock condition, energizing current is conducted from the positive voltage line through diode 146 to the feedback control relay coil 204 through the normally closed relay switch 186 of the second track control relay 194. The normally open relay switch 216 of relay 204 is thereby closed to complete an energizing circuit for the timer 210 to initiate a track changing operation as hereinbefore described stopping when the player head is positioned on the second track by opening the normally closed relay switch 186 through track control relay coil 194. The relay switch 186 being connected between diode 146 and relay switch 204, deactivates the'timer 210 to stop the track changing operation as well as to deenergize the relay coil 204. Similarly, track changing operations are initiated by closing of sensors 108 and connected through normally closed relay switches 188 and 190 to the relay coil 204 for activating the timer 210, track changing operation stopping on the tracks corresponding respectively to the track control relays 196 and 198. Any time the circuit is broken by opening of the sensor switches 106, 108 and 110, the tape player is deactivated anddisconnected from the pager system as compared to continued operation upon closing of the fire sensor 104 until reset.

The air of batteries 36 and 38 interconnected in series by the current limiting resistor 40, supplies power for the relay circuits and pager lines through a polarity reversing switch assembly 16 through which the system is reset and tested utilizing the same batteries. When the polarity reversing switch assembly is actuated, the positive terminal of battery 36 is transferred from voltage line 42 to voltage line 44 and the negative terminal to voltage line 42. The diodes 202, 136 and respectively connected between the timer 210, relay coil 134 and relay coil 124, prevent the relays from operating by blocking flow of current thereto. Reversed current can, however, flow through indicator lamp 114, in series with resistor 116, normally closed timer switch and diode 1 12 to the voltage line 42, thereby signifying that the sensing circuit 18 has continuity. The indicator lamp 114 will also be illuminated during normal opera tion when sensor 104 is activated. The player lamp 72 connected across the terminals of the player battery 54 by the relay switch 136 will furthermore signify operation of the tape player upon energization of relay coil 134. Both the player battery 54 and the relay alarm batteries may be monitored by a voltmeter 76 connected across the terminals of either source of voltage through the double throw, double pole switch 74.

Normally opened test switch 98 and normally closed test switch 96 are ganged in the test control 30. When actuated, the normally closed switch 96 is opened to disconnect the audio alarm system from all remote paging stations of the pager system through terminals 88 and 90 leaving only the local paging station operative through terminals 84 and 86. At the same time the mormally open test switch is closed to by-pass the sensing circuit 18 and energize the relay coil 124 in order to initiate operation of the audio alarm system as hereinbefore described, to provide an audio alarm only 10- cally for testing purposes.

Under normal operation, in the fire sensing mode, the relay coil 124 is latched by holding switch 126 in order to maintain operation even if the sensor 104 is opened. in order to conserve energy in this operational mode, the on-off timer 118 is energized simultaneously with relay coil 124, and is operative to intermittantly open and close the energizing circuit for relay coil 124 through the timer switch 122. Since the other sensing circuits conduct only as long as their sensors 106, 108 and 110 remain closed while detecting some condition, the current conducted is continuous as compared to the pulsating current of sensing circuit 18.

An electronic switch such as the FET 218 is connected between one terminal of the audio output winding of transformer 82 and terminal 84 to the paging system 32 in order to disconnect the audio alarm from the paging system when it is in use for intercommunication. The audio signal in the paging system when in use, is applied through resistor 220 to the control electrode of the FET 218 to switch it off.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. In combination with a record player having a player head displaceable relative to a plurality of tracks on a record medium from which different messages are reproduced, a plurality of sensors, a source of voltage, at least one self-latching circuit connected to said source of voltage for generating an intermittent player operating signal in response to actuation of one of the sensors, non-latching circuits connected to said source of voltage for generating continuous player operating signals in response to actuation of the other of the sensors, means for transmitting said signals to the record player to select the track at which the player head is positioned, interlock means for disabling the non-latching circuits in response to said intermittent player operating signal, reset means connected to said source of voltage for resetting the self-latching circuit in response to reversal in polarity of the source of voltage, and indicating means connected to said self-latching circuit for monitoring continuity thereof in response to said reversal in polarity.

2. In combination with a paging system adapted to establish intercommunication between a plurality of stations and a plural track record player connected to said paging system for reproducing a plurality of messages from different tracks of a record medium in response to detection of different corresponding conditions by a plurality of sensors; an audio alarm control system for regulating transmission of said messages to the paging system, including a plurality of sensing circuits connecting the sensors to the player for initating operation thereof, priority override means connected to said sensing circuits and responsive to activation of a selected one of the sensors for disabling the sensing circuits associated with the other of the sensors, the sensing circuits associated with the other of the sensors being interconnected in parallel for alternatively initiating operation of the player, one of the sensing circuits associated with said selected one of the sensors being connected to the player independently of the other of the sensing circuits and latching means connected only to said one of the sensing circuits for maintaining the player in operation following activation of said selected one of the sensors.

3. The combination of claim 2 including a source of electrical energy energizing the sensing circuits, polarity reversing means connecting the source to the sensing circuits for resetting said one of the sensing circuits in response to reversal of polarity of the source, means connected to said other of the sensing circuits for deenergization thereof in response to energization of said one of the sensing circuits, and indicator means activated in response to said polarity reversal for signifying circuit continuity of said one of the sensing circuits.

4. The combination of claim 3 including test means for simultaneously initiating operation of the record player in by-pass relation to the sensing circuits and localizing reproduction of a message in the paging system.

5. The combination of claim 4 including audio cut-off control means for disconnecting the player from the paging system in response to transmission of audio signals therethrough.

6. The combination of claim 5 including timing means for intermittantly interrupting energization of said one of the sensing circuits to conserve energy expended during operation of the player in response to activation of said selected one of the sensors.

7. The combination of claim 2 including test means for simultaneously initiating operation of the record player in by-pass relation to the sensing circuits and localizing reproduction of a message in the paging systern.

8. The combination of claim 2 including audio cut-off control means for disconnecting the player from the paging system in response to transmission of audio signals therethrough.

9. The combination of claim 3 including timing means for intermittantly interrupting energization of said one of the sensing circuits to conserve energy expended during operation of the player in response to activation of said one of the sensors.

10. The combination of claim 2 including timing means for intermittantly interrupting energization of said one of the sensing circuits to conserve energy expended during operation of the player in response to activation of said one of the sensors.

11. In combination with a paging system adapted to establish intercommunication between a plurality of stations and a plural track record player connected to said pagingsystem for broadcasting a plurality of messages from different tracks of a record medium in response to detection of different corresponding conditions by a plurality of sensors; an audio alarm control system for regulating transmission of said messages to the paging system, including a plurality of sensing circuits connecting the sensors to the player for initiating operation thereof, a source of electrical energy for energizing the sensing circuits, polarity reversing means connecting the source to the sensing circuits for resetting a selected one of the sensing circuits in response to reversal of polarity of the source, interlock means connected to said other of the sensing circuits for preergy expended during operation of the player in response to activation of said one of the sensors.

14. The combination of claim 2 wherein said record player includes a player head, means for displacing said player head to different positions operatively aligned with said tracks on the record medium, position sensing means connecting the record player to the sensing circuits for operating the displacing means to sequentially change the tracks with which the player head is aligned, and means responsive to activation of said sensors for selecting the tracks at which operation of the displacing means SIOPS. 

1. In combination with a record player having a player head displaceable relative to a plurality of tracks on a record medium from which different messages are reproduced, a plurality of sensors, a source of voltage, at least one self-latching circuit connected to said source of voltage for generating an intermittent player operating signal in response to actuation of one of the sensors, non-latching circuits connected to said source of voltage for generating continuous player operating signals in response to actuation of the other of the sensors, means for transmitting said signals to the record player to select the track at which the player head is positioned, interlock means for disabling the non-latching circuits in response to said intermittent player operating signal, reset means connected to said source of voltage for resetting the selflatching circuit in response to reversal in polarity of the source of voltage, and indicating means connected to said selflatching circuit for monitoring continuity thereof in response to said reversal in polarity.
 2. In combination with a paging system adapted to establish intercommunication between a plurality of stations and a plural track record player connected to said paging system for reproducing a plurality of messages from different tracks of a record medium in response to detection of different corresponding conditions by a plurality of sensors; an audio alarm control system for regulating transmission of said messages to the paging system, including a plurality of sensing circuits connecting the sensors to the player for initating operation thereof, priority override means connected to said sensing circuits and responsive to activation of a selected one of the sensors for disabling the sensing circuits associated with the other of the sensors, the sensing circuits associated with the other of the sensors being interconnected in parallel for alternatively initiating operation of the player, one of the sensing circuits associated with said selected one of the sensors being connected to the player independently of the other of the sensing circuits and latching means connected only to said one of the sensing circuits for maintaining the player in operation following activation of said selected one of the sensors.
 3. The combination of claim 2 including a source of electrical energy energizing the sensing circuits, polarity reversing means connecting the source to the sensing circuits for resetting said one of the sensing circuits in response to reversal of polarity of the source, means connected to said other of the sensing circuits for deenergization thereof in response to energization of said one of the sensing circuits, and indicator means activated in response to said polarity reversal for signifying circuit continuity of said one of the sensing circuits.
 4. The combination of claim 3 including test means for simultaneously initiating operation of the record player in by-pass relation to the sensing circuits and localizing reproduction of a message in the paging system.
 5. The combination of claim 4 including audio cut-off control means for disconnecting the player from the paging system in response to transmission of audio signals therethrough.
 6. The combination of claim 5 including timing means for intermittantly interrupting energization of said one of the sensing circuits to conserve energy expended during operation of the player in response to activation of said selected one of the sensors.
 7. The combination of claim 2 including test means for simultaneously initiating operation of the record player in by-pass relation to the sensing circuits and localizing reproduction of a message in the paging system.
 8. The combination of claim 2 including audio cut-off control means for disconnecting the player from the paging system in response to transmission of audio signals therethrough.
 9. The combination of claim 3 including timing means for intermittantly interrupting energization of said one of the sensing circuits to conserve energy expended during operation of the player in response to activation of said one of the sensors.
 10. The combination of claim 2 including timing means for intermittantly interrupting energization of said one of the sensing circuits to conserve energy expended during operation of The player in response to activation of said one of the sensors.
 11. In combination with a paging system adapted to establish intercommunication between a plurality of stations and a plural track record player connected to said paging system for broadcasting a plurality of messages from different tracks of a record medium in response to detection of different corresponding conditions by a plurality of sensors; an audio alarm control system for regulating transmission of said messages to the paging system, including a plurality of sensing circuits connecting the sensors to the player for initiating operation thereof, a source of electrical energy for energizing the sensing circuits, polarity reversing means connecting the source to the sensing circuits for resetting a selected one of the sensing circuits in response to reversal of polarity of the source, interlock means connected to said other of the sensing circuits for preventing energization thereof in response to energization of said selected one of the sensing circuits, and indicator means activated in response to said polarity reversal for signifying circuit continuity of said selected one of the sensing circuits.
 12. The combination of claim 11 including test means for simultaneously initiating operation of the record player in by-pass relation to the sensing circuits and localizing reproduction of a message in the paging system.
 13. The combination of claim 11 including timing means for intermittantly interrupting energization of said selected one of the sensing circuits to conserve energy expended during operation of the player in response to activation of said one of the sensors.
 14. The combination of claim 2 wherein said record player includes a player head, means for displacing said player head to different positions operatively aligned with said tracks on the record medium, position sensing means connecting the record player to the sensing circuits for operating the displacing means to sequentially change the tracks with which the player head is aligned, and means responsive to activation of said sensors for selecting the tracks at which operation of the displacing means stops. 